1. Field of the Invention
The present invention relates generally to perpendicular recording of data onto magnetic recording disks.
2. Description of the Related Art
In data recording devices such as magnetic disk drives and tape drives, MR and GMR heads are used to read data that has been recorded on the devices. These heads detect magnetic transitions on the storage medium that have been previously established (xe2x80x9cwrittenxe2x80x9d) on the medium to represent data. The output voltage waveform of the head represents the transition locations and, thus, the data on the medium.
The magnetic transitions can be thought of as vectors, and in conventional magnetic recording, the direction of each magnetic transition vector, i.e., the angle of magnetization, is parallel to the recording track. This is also referred to as xe2x80x9clongitudinalxe2x80x9d recording. More recently, perpendicular recording has been proposed, wherein the angle of magnetization is more or less perpendicular to the recording track. Actually, the present invention recognizes that the angle of magnetization deviates from the true perpendicular by an amount that depends on the distance between magnetic transitions. In any case, one advantage of perpendicular recording over longitudinal recording is that perpendicularly-recorded disks are more thermally stable than longitudinally-recorded disks.
As recognized herein, however, much work over the years has been spent on developing read signal processing that assumes longitudinal recording. Accordingly, the present invention recognizes that it would be advantageous to provide a way to process perpendicular magnetic transition signals in a manner that could exploit the well-developed technology in longitudinal recording read channels. Moreover, the present invention recognizes that timing recovery information can be extracted from the instantaneous phase/frequency of the complex analytic signal obtained by means of a Hilbert transform of the perpendicular readback signal.
A magnetic data read device for processing signals from a perpendicularly-recorded magnetic storage medium includes at least one Hilbert transform that receives signals from the magnetic storage medium. In a preferred embodiment, a read channel cooperates with the Hilbert transform. The Hilbert transform can be between the read channel and the storage medium, or it can be located in the read channel, before or after the ADC of the read channel.
One preferred Hilbert transform can be established by a finite impulse response (FIR) having plural taps. For instance, the FIR can have at least five taps, and indeed can have seven taps. In any case, the signals received from the storage medium are perpendicular signals, the read channel includes at least one equalizer, and the Hilbert transform cooperates with the equalizer to transform the perpendicular signals to longitudinal signals.
In another aspect, a computer program device includes a computer readable medium having a program of instructions thereon for processing data associated with a magnetic recording medium. The program of instructions includes logic means for determining a magnetization angle from a complex analytic signal established by combining a Hilbert transformation of a magnetic recording read signal with the read signal.
In still another aspect, a method is disclosed for determining an angle of magnetization on a perpendicular recording medium. The method includes receiving a signal from the medium, and deriving a Hilbert transform of the signal. The Hilbert transform of the signal is combined with the signal to render a complex analytic signal.
In another aspect, a method for determining an angle of magnetization on a perpendicular recording medium includes receiving a signal from the medium, deriving a Hilbert transform of the signal, and, using the Hilbert signal, deriving the angle of magnetization.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: